Expand all the collapsed fragments in the file up to the specified nesting level

Fold Selection / Remove region

Ctrl+Period

Collapse the selected fragment and create a custom folding region for it to make it "foldable" /
Expand the current fragment and remove the corresponding custom folding region to make the fragment "unfoldable"

Fold Code Block

Ctrl+Shift+Period

Collapse the code fragment between the matched pair of curly braces {} and
create a custom folding region for that fragment to make it "foldable"